According  to the  World  Health   Organization, consumption  of table  salt(being  a major carrier  of iodine  in human  diet)  should  be  reduced  of 50%.  Vegetables biofortified  with iodine can become an  alternative source of this  element  for humans.  Agronomic recommendations  with   reference to biofortification   have  to be  developed,  including  the  evaluation  of side-effects  associated  with  iodine application   to plants.   Iodine  is  not  an essential element  for  plants  and  hence its  effect  on crops  has  not  yet been  diagnosed.  The  aim  of the  study has been to assess  the  influence of soil  fertilization with  KI and  foliar  application  of KIO3 on the  success  of iodine  biofortification   as  well  as  the  mineral  composition  of lettuce. Lettuce  cv.  Melodion F1 was  cultivated   in a  field experiment  in 2008-2009.  Combinations  with  different   soil  fertilization and  foliar nutrition with iodine  were  distinguished in  the  research  including: control  (without iodine application), three  combinations  with  presowing  soil  fertilization of iodine (in the  form  of KI) in  doses of 0.5,  1.0  and  2.0  kg I ha-1 as  well  three combinations  with   four  applications   of foliar   nutrition  with   iodine solution (as KIO3) in  the  concentration  of:  0.0005%,  0.005%  and  0.05%  after using  1000 dm3   of working  solution  per  1  ha  so that  the  following amounts  of iodine  were applied:  0.02,  0.2 and  2.0  kg  I ha-1, respectively. In  lettuce  heads,  the  iodine content  as  well  as  the  content of: P, K, Mg, Ca,  S, Na,  B, Cu,  Fe,  Mn,  Zn, Mo, Al,  Cd  and  Pb  were  determined using  the ICP-OES technique,  while  N-total  was  assayed  by  Kjeldahl method.  In  comparison  to the control,  only  foliar nutrition with  0.05% solution  of iodine  significantly improved  accumulation  of this element  in lettuce.  At  the  same  time,  a  lower  level  of nitrogen  nutrition  was observed in  plants  from  this  combination.  A significant  increase in  the  N-total content  was found only  in  lettuce  plants  fed with  2.0  kg  I ha-1  dose of KI. In reference  to the  control, both foliar  and  soil  application  of iodine contributed  to a  higher  content  of K, Mg,  Ca,  Mn and  Cd  as  well  as  a decreased  level  of P, Cu  and  Zn  in  lettuce. Doses,  forms  and  application methods  of iodine were found  to  have  produced  diverse  effects  on  the content  of S, Na,  B, Fe, Mo, Al  and Pb in lettuce  plants.